Shares slumped 4% in after-hours trading. If the decline holds through the opening bell – which of course is no guarantee – IBM alone would subtract about 51 points off the price-weighted Dow.

It’s not just IBM that is poised for a big tumble. Shares of Google, which aren’t in the Dow but have a big influence in the S&P 500 and the Nasdaq Composite, are set to fall after the Internet-search giant’s first-quarter results disappointed investors. Expenses outpaced revenue growth, while the amount Google earned per click dropped 9%, continuing a trend where the company’s clicks have become less valuable.

Large-cap tech stocks have generally held up better than the smaller so-called momentum stocks that have been hit hard over the past several weeks. IBM, for instance, has risen 4.7% this year through Wednesday’s close, while the tech-heavy Nasdaq Composite is off 2.2%. Popular consumer Internet companies have been hit hardest; Facebook is down 17% from its record close in early March. Netflix and Twitter are off 27% and 39%, respectively, from their all-time highs earlier this year. Even Google has felt the pain; the stock has been one of the biggest drags on the Nasdaq since March 1.

What’s more, IBM’s slide could foreshadow a tough stretch for the broad market over the next several weeks.

Since 2001, IBM’s one-day reaction to its quarterly report has been a fairly accurate predictor of the overall market’s near-term direction. When IBM shares have dropped after earnings, the S&P 500 has averaged a 2.3% decline over the next five weeks, according to Bespoke Investment Group. When IBM shares have risen following quarterly results, the S&P 500 has gained 1.4%, on average, five weeks later.

The S&P 500 on Wednesday edged back into positive territory for the year, up 0.8%. But the rally may prove short-lived, thanks to IBM and Google.

Morning MoneyBeat Daily Factoid: On this day in 1961, the U.S. unsuccessfully attacked Cuba at the Bay of Pigs invasion in an attempt to overthrow Fidel Castro.

STOCKS TO WATCH

Goldman Sachs is projected to report first-quarter earnings of $3.49 a share, according to a consensus survey by FactSet. Read: Goldman Sachs earnings preview.

General Electric is forecast to report first-quarter earnings of 32 cents a share.

Morgan Stanley is expected to post first-quarter earnings of 61 cents a share. Read: What investors can expect from Morgan Stanley.

PepsiCo is projected to report earnings of 75 cents a share in the first quarter.

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